Attempts to substitute polyvinyl chloride (PVC) with other materials are actively underway in a variety of industries. However, development of proper substitutes is limited due to various reasons related to fire retardancy as one advantage of polyvinyl chloride. In particular, in preparing electric wires such as cables, it is not easy to realize fire retardancy of polyvinyl chloride using a substitute for polyvinyl chloride.
Regulations regarding fire retardancy are based on UL (Underwriters Laboratories) standards, and, in preparing a resin composition, particularly a thermoplastic resin composition, having suitable fire retardancy satisfying UL standards, a halogen-based fire retardant and a fire retardant are generally kneaded in a thermoplastic resin. Polybromodiphenylether, tetrabromobisphenol A, an epoxy compound with a bromine substituent, chlorinated polyethylene, etc. have been mainly used as the halogen-based fire retardant. As the fire retardant, antimony-based compounds are used and, thereamong, antimony trioxide and antimony pentoxide are generally used.
As described above, when fire retardancy is provided to a thermoplastic resin by applying a halogen-based fire retardant and antimony-based fire retardant together, excellent fire retardancy is exhibited and a thermoplastic resin composition, which may produce final products without almost no property deterioration, may be prepared. However, upon processing, hydrogen halide gas is generated and thus a mold may be damaged. In addition, upon discarding, dioxin having strong carcinogenicity is discharged from a waste incinerator due to the presence of a halogen compound, thus harmfully affecting the environment and the human body. Furthermore, regulations on use of halogen-based fire retardant resin materials are actively applied in Europe, and thus, development of a fire retardant thermoplastic resin composition not comprising halogen is required.
In order to provide fire retardancy to a thermoplastic resin composition not comprising halogen, aromatic phosphorus-based ester compounds are generally used. When such a phosphorus-based ester compound is applied alone, heat resistance of a thermoplastic resin is decreased and it is difficult to accomplish desired fire retardancy. Accordingly, in order to enhance heat resistance of a thermoplastic resin and provide fire retardancy thereto, a method of applying a phosphoric ester compound blended with polyphenylene ether has been suggested and studied.
In an embodiment, Korean Patent Application Pub. No. 10-2013-0121152 discloses a polyphenyl ether elastomer composition. The polyphenyl ether elastomer composition comprises 10 to 46 parts by weight of polyphenylether, 3 to 5 parts by weight of polystyrene, 3 to 5 parts by weight of polystyrene having superior impact resistance, 6 to 13 parts by weight of polyolefin elastomer, 13 to 23 parts by weight of a hydrogenated styrene-butadiene block copolymer, 6 to 16 parts by weight of low-density polyethylene, 5 to 8 parts by weight of a low-density polyethylene graft polystyrene copolymer and 18 to 20 parts by weight of a phosphate fire retardant. In addition, Korean Patent Application Pub. No. 10-2010-0017356 discloses a fire retardant thermoplastic composition and a product comprising the same. The fire retardant thermoplastic composition comprises poly(arylene ether), block copolymer, liquid polyolefin and a fire retardant additive. The fire retardant additive composition comprises phosphate selected from the group consisting of metal hydroxide, organic phosphate and melamine phosphate, melamine pyrophosphate, melamine orthophosphate, melem polyphosphate, melam polyphosphate, diammonium phosphate, monoammonium phosphate, amide phosphate, melamine polyphosphate, ammonium polyphosphate, amide phosphate and a combination of two or more thereof.
Poly arylene ether comprising the polyphenylene ether is an amorphous resin and has advantages such as superior fire retardancy, insulating properties, heat resistance, rigidity, etc. Poly arylene ether modified from the poly arylene ether has substantial advantages in regard to fire retardancy. However, since poly arylene ether has high processing temperature, fire retardant types which may be used are greatly limited. In addition, when a fire retardant is added, in an amount of greater than a certain range, to a thermoplastic resin composition comprising the polyphenylarylene ether, there are problems in dispersion of a fire retardant upon processing into electric wires such as cables, and a fire retardant is protruded to a surface of a product that is processed and molded, thereby deteriorating product appearance and quality. Accordingly, the total amount of a fire retardant added is limited. In particular, upon extrusion, various problems related to appearance are more likely to occur.
Therefore, there is still a need for development of a fire retardant thermoplastic resin composition that is suitable for preparation of an electric wire, etc. by addressing conventional problems and enhancing extrudability of a resin composition without decreasing fire retardancy of the resin composition.